noise in go lang

main.go

package main

import _ "image/png"

import (
  "os"
  "image"
  "image/draw"
  "image/color"
  "image/png"
  "math/rand"
  "fmt"
)

func main() {
  m := image.NewRGBA(image.Rect(0, 0, 640, 480))
  black := color.RGBA{0, 0, 0, 255}
  draw.Draw(m, m.Bounds(), &image.Uniform{black}, image.ZP, draw.Src)
  toimg, _ := os.Create("new.png")
  defer toimg.Close()
  w := m.Bounds().Max.X
  h := m.Bounds().Max.Y
  fmt.Println("w", w, "h", h)
  x := 0
  y := 0
  n := 1000000
  prev := color.RGBA{0, 0, 0, 0}
  for i := 0; i < n; i++ {
    x = rand.Intn(w)
    y = rand.Intn(h)
    prev = m.At(x, y).(color.RGBA)
    prev.R += 30
    m.Set(x, y, prev)
  }
  png.Encode(toimg, m)
}